An aqueous -solvent based process for continuous manufacturing of supported ion selective membranes

Abstract

A membrane, for example an ion exchange membrane, is made by preparing a curable liquid using at least one aqueous solvent. The curable liquid is continuously cast onto a substrate to form a membrane precursor. The membrane precursor is continuously cured to form a membrane. Optionally, the curable liquid may be made by mixing a water soluble aliphatic sulfonic acid monomer with a pair of crosslinking monomers and a water soluble free-radical generating catalyst. Optionally, the method may include one or more steps of processing the membrane.

What is claimed is: 
     
         1 . A method for manufacturing a membrane, the method comprising:
 a. preparing a curable liquid with an aqueous solvent;   b. casting a membrane precursor; and   c. curing the membrane precursor to form a membrane,   wherein the step (b) comprises introducing the curable liquid into a film pocket and wetting a substrate, and wherein the steps (b) and (c) operate continuously.   
     
     
         2 . The method of  claim 1 , wherein the step (a) comprises mixing a water soluble aliphatic sulfonic acid monomer with a pair of crosslinking monomers and a water soluble free-radical generating catalyst. 
     
     
         3 . The method of  claim 2 , wherein the water soluble, aliphatic sulfonic acid monomer is selected from a group consisting of 2-acrylamido-2-methylpropane sulfonic acid, sulfoethyl methacrylate, and sulfopropyl methacrylate. 
     
     
         4 . The method of  claim 2 , wherein the pair of crosslinking monomers are selected from the group consisting of acrylamide paired with N-methylolacrylamide and methacrylamide paired with N-methylolmethacrylamide. 
     
     
         5 . The method of  claim 1 , wherein the step (a) comprises mixing a solution of a bifunctional methylenebisacrylamide monomer with an ionogenic acrylic monomer and a water soluble, free-radical generating catalyst. 
     
     
         6 . The method of  claim 5 , wherein the ionogenic acrylic monomer is selected from a group consisting of compounds with the following formula: 
       
         
           
           
               
               
           
         
         wherein: 
         R=H, CH 3 ; 
         R 1 =C 1 -C 22 ; 
         R 2 , R 3 , R 4 =H, CH 3 , alkyl containing C 2 -C 22 , benzyl, phenyl; and
   X − =Cl − ,Br − ,½SO4 − ,NO3 − .
 
 
       
     
     
         7 . The method of  claim 5 , wherein the ionogenic acrylic monomer has the following formula: 
       
         
           
           
               
               
           
         
       
     
     
         8 . The method of  claim 1 , wherein the step (a) comprises mixing a water soluble, ionic, cross-linking monomer and a water soluble, free-radical generating catalyst. 
     
     
         9 . The method of  claim 8 , wherein the water soluble, ionic, crosslinking monomer is a product of mixing a glycidyl ester, an ionogenic methacrylate ester and a water soluble acid, wherein the ionogenic methacrylate ester comprises a vinyl group and a tertiary amine group and wherein the water soluble, ionic, cross-linking monomer has the following formula: 
       
         
           
           
               
               
           
         
       
     
     
         10 . The method of  claim 8 , further comprising adding an ionogenic methacrylate ester monomer to the curable liquid. 
     
     
         11 . The method of  claim 1 , wherein the step (a) comprises mixing a tertiary amine, an acid, and a polyepoxide. 
     
     
         12 . The method of  claim 11 , wherein the tertiary amine is selected from a group consisting of dimethylaminopropylmethacrylamide, dimethylaminopropyl acrylamide, diethylaminopropylmethacrylamide, dimethylaminoethyl methacrylate, and mixtures thereof. 
     
     
         13 . The method of  claim 11 , wherein the polyepoxide is selected from the group consisting of diethylene glycol diglycidyl ether; diglycidyl 1,2-cyclohexanedicarboxylate; N,N-diglycidyl-4-glycidyloxyaniline; bisphenol A diglycidyl ether; brominated bisphenol A diglycidyl ether; bisphenol F diglycidyl ether; 1,4-butanediol diglycidyl ether; 1,4-butanediyl diglycidyl ether; 1,4-cyclohexanedimethanol diglycidyl ether; glycerol diglycidyl ether; resorcinol diglycidyl ether; bis[4-(glycidyloxy)phenyl]methane; bisphenol A propoxylate diglycidyl ether; dimer acid diglycidyl ester; ethylene glycol diglycidyl ether; brominated neopentyl glycol diglycidyl ether; diglycidyl ether-terminated poly(dimethylsiloxane); poly(ethylene glycol)diglycidyl ether; poly(propyleneglycol)diglycidyl ether; 1,2,3-propanetriol glycidyl ether; 1,3-butanediol diglycidyl ether; tris(2,3-epoxypropyl)isocyanurate; trimethylolpropane triglycidyl ether; tris(4-hydroxyphenyl)methane triglycidyl ether 2,6-tolylene diisocyanate; tris(4-hydroxyphenyl)methane triglycidyl ether; glycerol propoxylate triglycidyl ether; trimethylolethane triglycidyl ether; 1,3-butadiene-diepoxide; 1,3-butadiene diepoxide; dicyclopentadiene dioxide; and methyl cis,cis-11,12,14,15-diepoxyeicosanoate. 
     
     
         14 . The method of  claim 11 , further comprising adding an ethylenic monomer to the curable liquid. 
     
     
         15 . The method of  claim 14 , wherein the ethylenic monomer is selected from a group consisting of methacrylamine; N-methylmethacrylamide; N-vinyl pyrrolidone; N-vinyl caprolactam; methacrylamidopropyl trimethylammonium chloride; and trimethylammoniumethyl methacrylate chloride. 
     
     
         16 . The method of  claim 11 , further comprising adding a water soluble, free-radical generating catalyst. 
     
     
         17 . The method of  claim 1 , wherein the step (a) comprises mixing a primary crosslinker with a secondary crosslinker, wherein the primary crosslinker comprises a crosslinked ionic monomer that comprises a quaternary ammonium group. 
     
     
         18 . The method of  claim 17 , wherein the crosslinked ionic monomer is a product of mixing polyepoxide with a tertiary amine including an acrylic group in the presence of an acid. 
     
     
         19 . The method of  claim 17 , wherein the primary crosslinked ionic monomer has the formula: 
       
         
           
           
               
               
           
         
         wherein: 
         R is —[CH 2 —CH(OH)] 2 —W; 
         R 1  is hydrogen or a C 1 -C 12  alkyl group; 
         Z is oxygen or N—R 3 ; R 2  is —[CH 2 ] n —; 
         R 3  is hydrogen or —[CH 2 ] m —CH 3 ; 
         R 4  and R 5  are each, independently, —[CH 2 ] m —CH 3 ; 
         X is selected from the group consisting of Cl, Br, I and acetate; 
         W is a bridging group or atom; 
         m is an integer from 0 to 20; and 
         n is an integer from 1 to 20. 
       
     
     
         20 . The method of  claim 17 , wherein the secondary crosslinker is prepared by mixing an acrylamide compound with another acrylamide compound including hydroxyl groups. 
     
     
         21 . The method of  claim 1 , further comprising (d) processing the membrane comprising conveying the membrane through at least two processing areas. 
     
     
         22 . The method of  claim 21 , further comprising conveying the membrane precursor from a processing area for step (c) to a processing area for step (d). 
     
     
         23 . The method of  claim 22 , further comprising conveying the substrate through processing areas for step (b) to the processing area for step (c). 
     
     
         24 . The method of  claim 21 , wherein the step (d) further comprises extracting residues from the membrane and washing the membrane. 
     
     
         25 . The method of  claim 24 , wherein, following the steps of extracting the residues from the membrane and washing the membrane, step (d) further comprises:
 applying a dye to a first surface of the membrane;   feeding a contrast material adjacent a second surface of the membrane;   identifying dye marked regions of the contrast material; and   cutting the membrane.   
     
     
         26 . The method of  claim 1 , wherein the aqueous solvent comprises water.